Pyrolysis waste and biomass treatment

ABSTRACT

The present invention provides methods and apparatus for treating waste, such as municipal waste via pyrolysis and yielding one or more of heat energy, electrical energy and fuel. In some embodiments, waste feed stock can be municipal waste in black bag form. In some the present invention additionally provides for processing of thousands of tons of municipal waste each day.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to pending patent applicationSer. No. 12/816,632, filed Jun. 16, 2010, entitled, “Pyrolysis Waste andBiomass Treatment,” as a Divisional Patent Application, the contents ofwhich are relied upon and incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to methods and apparatus for convertingone or both of mixed waste and biomass into electrical energy. Morespecifically, the present invention presents methods an apparatus forprocessing waste, such as for example municipal solid waste and biomass,in a pyrolysis chamber that will create a synthetic gas that can be usedto generate electrical power with the use of an electrical generator,turbine or other power generating equipment.

BACKGROUND OF THE INVENTION

Traditional methods of dealing with municipal solid waste generallyincluded one of two alternatives: a) is the waste was burned; or b) thewaste was buried. However, landfills and incineration are no longerpreferred or even viable solutions due to diminishing area available,environmental concerns and cost to develop/maintain. A landfill capableof servicing a mid size municipality may run into the hundreds ofmillions of dollars and an approval process may take ten or fifteenyears. Once in operation, the full life of a landfill may be shorteneddue to environmental concern.

Incineration of waste creates greenhouse gases which are being targetedto be reduced, thus processes that produce them are being considered tobe unacceptable. In the United States, the number of operating landfillshas diminished significantly over the last several decades.Consequently, alternative ways of dealing with municipal waste must besought.

It is known for biomass to be treated with Pyrolysis or similar heatingmethods that limit an amount of oxygen available to the waste andthereby eliminate combustion, such as, for example the system describedin U.S. Pat. No. 7,293,511. In some known processes an oil, is generatedwhich may be burned in a relatively clean fashion. Conditions forproducing pyrolysis oil will typically include virtually no oxygen.Pyrolysis oil or other thermo-chemically-derived biomass liquids can beused directly as fuel, or sometimes as a platform to produce chemicalsand materials.

Currently known Pyrolysis machines include a heat chamber and a heatsource located around the periphery of the heating chamber. Althoughthese units provide a proof of concept to a basic science of conversionof biomass to a usable product, their effectiveness has only beenapplicable for relatively homogeneous biomass, such as byproducts of apaper mill, and only for modest amounts of biomass conversion. Inaddition, the efficiency of these known types of pyrolysis units isgenerally less than desirable.

Fast pyrolysis includes thermal decomposition of a biomass fuel atmoderate temperatures with a relatively high heat transfer rate to thebiomass particles and a short hot vapor residence time in a reactionzone. Several reactor configurations have been shown to assure suchconditions and to achieve yields of a burnable liquid byproduct. Designsof such pyrolysis apparatus may include bubbling fluid beds, circulatingand transported beds, cyclonic reactors, and ablative reactors.

Biomass pyrolysis research has been directed to vortex (cyclonic) andfluidized bed reactors for processing biomass via pyrolysis. Thefluidized bed reactor of the Thermo chemical Users Facility at theNational Renewable Energy Laboratory is a 1.8 m high cylindrical vesselof 20 cm diameter in the lower (fluidization) zone, expanded to 36 cmdiameter in the freeboard section. It is equipped with a perforated gasdistribution plate and an internal cyclone to retain entrained bed media(typically sand). The reactor is heated electrically and can operate attemperatures up to 700° C. at a throughput of 15-20 kg/h of biomass.

Some experimental pyrolysis technologies have been demonstrated whichutilize circulating fluidized bed plants. However, each of the fluidizedbed plant models requires homogeneous biomass and can only scale to asize too small to function effectively for a municipality. Generally,the previously known pyrolysis machines expose biomass to 550° C., in anoxygen-deprived environment and do not provide an adequate amount ofheat transfer area for a uniform amount of heat to consistently treatmunicipal waste.

Accordingly, new apparatus and methods are needed to efficiently treatmunicipal waste on a scale suitable for a small city or waste processingarea.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides the methods and apparatusfor providing a pyrolysis waste treatment to clean energy system in anenvironmentally friendly manner. In preferred embodiments, the “waste”includes mixed municipal waste, although other forms of waste, such as,for example, one or more of solid waste from a water treatment plant,homogenous waste, and biomass may also be utilized.

In some embodiments of the present invention, apparatus and methods areprovided which are capable of converting fifteen hundred (1,500) tons ormore of municipal solid waste into about seven hundred eighty seven(787) megawatts of electricity per day. Generally, to place this inperspective, 787 megawatts per day is enough electricity to powerapproximately thirty thousand (30,000) homes each day.

In one aspect the present invention provides a pyrolysis unit withincreased efficiency. The pyrolysis unit specifically includes a muffleand a heat source. In preferred embodiments, the heat source includes acombustion chamber, capable of burning gas resulting from the exposingof municipal waste to pyrolysis. Other heat sources may include, forexample, electrical heaters. According to the present invention, themuffle and multi zoned heat tube configuration increases the heatedsurface area to which the waste is exposed. The increased exposure ofheat throughout the muffle provides for more uniform and completepyrolysis of the waste material feed stock placed into the muffle whilealso decreasing the amount of retention time that the waste materialfeed stock must be within the muffle in order to be adequatelyprocessed.

In another aspect, multiple pyroliser retorts may be joined together toform a single pyrolysis unit for processing one or more of: municipaland commercial and industrial waste.

BRIEF DESCRIPTION OF THE DRAWINGS

As presented herein, various embodiments of the present invention willbe described, followed by some specific examples of various componentsthat can be utilized to implement the embodiments. The followingdrawings facilitate the description of some embodiments:

FIG. 1 illustrates a pyrolysis unit within a waste processing facilityaccording to some embodiments of the present invention.

FIGS. 2A-2G illustrate various views of aspects of some embodiments of apyrolysis unit according to the present invention.

FIG. 3 illustrates some exemplary method steps that may be implementedaccording to the present invention.

DETAILED DESCRIPTION

The present invention provides methods and apparatus for convertingmunicipal solid waste into electrical energy on a scale commensuratewith urban and suburban needs. Generally, the methods and apparatusdescribed herein eliminate the need for manual presorting of garbage andcan accommodate thousands of tons a day of unprocessed “black-bag”garbage or construction debris. The present invention provides for theproduction of high calorific value fuel, which can be used in gas runturbines to produce electricity. The fuel can also be used inCogeneration/Combined Heat and Power (CHP) technology to produce notonly electricity, but also other useful heat; which may be seen as anincreasingly valuable resource. The present invention is scalable suchthat although size, quantities and volumes are generally described toprocess approximately fifteen hundred tons of municipal waste per day,such sizes, quantities and volumes may be scaled or duplicated toprovide greater or smaller volumes of processing.

The methods and apparatus presented herein generally relate to thermalprocessing of municipal waste in an oxygen deprived environment whichstifles combustion during the thermal processing. A pyrolysis gas orliquid fuel byproduct is produced which may be used to power turbines,or other power generating equipment, and generate heat used for theprocess and also provide electrical energy to a power grid connected toa plant operating according to the concepts provided herein.

After autoclaving and separation, the refuse derived fuel (rdf)extracted from the municipal solid waste is dried and sized, and then isinput into pyrolysis chambers and pyrolyzised. In the pyrolysischambers, the waste is exposed to heat of between 500° C. and 800° C. inan atmosphere containing no oxygen such that combustion is avoided. Theresulting gas is then passed through a series of cyclones, a heatexchanger, condensers and gas scrubber where any solids and condensatesare removed. Any non converted rdf is transferred to the residuereduction chambers at the base of the pyrolysis chambers where it isused for raising steam and assisting with heating of the pyrolysischambers. The cleaned gas is stored in gas storage tanks, prior to usefor running the gas engines etc, and the burners throughout the system.Loading, processing, offloading and cleaning may be controlled by aprogrammable logic controller (plc) and is supported by a fullyintegrated automation system.

Definitions

As used herein, MSW refers to municipal solid waste also called urbansolid waste, means one or more of household (domestic waste), commercialand institutional waste materials. A MSW may be in one or both of solidand semisolid form and generally exclude industrial hazardous wastes,wherein an industrial hazardous waste may be considered a waste productof an industrial process that may cause, or significantly contribute to,an increase in mortality (death) or an increase in serious irreversible,or incapacitating reversible illness; or pose a substantial (present orpotential) hazard to human health or the environment when improperlytreated, stored, transported, or disposed of, or otherwise managed.

As used herein, REC refers to renewable energy center such as, forexample a location where researchers and businesses interested inadvancing, developing, and using alternative energy technologies andrelated applications.

As used herein, I&C waste refers to industrial and commercial wastewhich is a general reference to a different kind of dry waste, such asoffice waste, product packaging waste, production waste and the like.

As used herein, a dryer refers to an appliance or piece of equipmentthat removes moisture by heating or another process.

As used herein, a muffle refers to a single unit with baffles.

As used herein, RDF is Refuse Derived Fuel. RDF is produced byprocessing one or both of MSW and other feedstock to increase the fuelvalue of the waste. The processing removes incombustible materials suchas dirt, glass, metals, etc, and it makes RDF more consistent in sizethan raw MSW.

As used herein, gasholder is a large container where gas is stored forsystem use.

As used herein, a retort is an enclosed piece of equipment that willcollect the omitted gases from the process.

As used herein, bag filter recovers particulate matter from exhaust gasto recover product and reduce air emissions or violate air pollutionstandards. The bag filter includes housing, filter bags, cleaning andair bleed assembly.

As used herein, gasometer is a large container where gas is stored forsystem use.

Referring now to FIG. 1, MSW, I & C waste or other feedstock 101 is fedinto a pre-conditioner, such as, for example an autoclave 102. Thepre-conditioner may be used to preheat biomass. Partial volatilizationmay be carried out within the pre-conditioner. The pre-conditioner mayinclude, for example, an indirectly heated, rotary drum typepre-pyrolysis unit.

MSW or I&C may enter the pre-pyrolysis unit in black garbage bags orother raw form and exit the pre-pyrolysis unit in a form resembling thetexture and appearance of potting soil. The pre-pyrolysis unit may beoperated at temperature suitable to a particular waste feedstock. ForMSW a suitable temperature is generally at a nominal temperature ofabout 500° C., however, generally temperatures of between 400° C. and600° C. may be used.

In some embodiments, an ingress of air into the unit is prevented orlimited. Limited air decreased the opportunity for combustion, in someembodiments, a maintenance of a high organic waste bed level in the feedhopper, this design is a driven screw feeder the compression of thewaste within screw feeder the nitrogen bleed to the screw. The screwfeeder may be interlocked to prevent the feed level contained in thehopper falling below a pre-determined level. An exit of the drum may belocated, for example, directly above the pyrolysis where the exitingmaterial falls directly into the dry pyrolysis.

One or both of exiting MSW and I&C pre-conditioned material istransported, such s, for example via a conveyor or other automatedcarrying device to a sifting section, such as a mechanical screeningdevice with a sifting screen. The sifting screen separates out theorganic cellulosic grains or flakes from the larger inorganic matter,such as, aluminum, magnetic metals and plastics. Heavier aluminum andmagnetic metals may be separated for recycling. Lighter weight plasticscan be shredded or ground into a size and shape suitable as feedstockfor the pyrolysis unit.

One or more of preheated and partially carbonized feed and fiber 103 andthe volatiles created in the pre-pyrolysis are fed to a dryer 104 wherethey are dried and discharged into the top of the pyrolysis muffle.Pyrolysis 105 occurs within a pyrolysis unit fed by the pyrolysismuffle.

During its passage under gravity to the base of the pyrolysis nearcomplete carbonization of the fiber occurs, releasing additionalvolatile gases present in the feed. Multiple radiant tubes are containedwithin the retort. This provides increased retention time of the productin the heated muffle and importantly increases and more uniformly allowradiant heat exposure to the product to pyrolise.

Conventional plate systems rely on the walls to provide the heat sourcedirectly to the material adjacent to the walls leaving the material notin direct contact not at the same temperature whereas the presentinvention provides for radiation heat throughout the muffle uniformlyheating product to maximize efficiency and product yield.. The syntheticgas produced from this heating process is discharged from the muffle viaports located along its length to be collected into a common, externalmanifold (106). To maintain a constant temperature profile, the furnaceannulus external to the muffle is divided into a number of control zonesof automatic temperature control. To ensure atmosphere integrity withinthe muffle, it may be operated at a slight positive pressure and theexit screw may incorporate a nitrogen bleed

In some embodiments, an additional muffle that may be located within theexhaust stack from the pyrolysis. This heating opportunity is tocomplete any partially oxidated tar-carbon impregnated ash exiting boththe pyrolysis and the expansion chamber to produce mainly oxides ofcarbon and hydrogen. Heat source for this muffle is steam via liveinjection.

Hot tar and particle laden synthetic gas is discharged from an externalmanifold into the top of an expansion chamber, where the design willcause a dramatic reduction in gas velocity. The gas's ability to carrytar laden particulate in suspension will be significantly reduced whenprecipitation of the latter onto an internal surface of the unit occurs.The unit incorporates, externally located, and pneumatically operatedhammers to minimize particulate buildup on the walls. The base of theunit serves as a temporary depository for tar impregnated particulateash matter that is deposited in the adjacent coolers. A screw conveyor,located in the base of the unit, then removes the accumulated materialand delivers it to the top of the exhaust stack muffle for furtheroxidation.

Synthetic gas is discharged from the expansion chamber, via isolationvalves, into one of two cooling chambers, each of which is able tohandle the entire gas flow independently. Both chambers incorporatewater cooled panels and a screw conveyor to transfer one or both of thecondensed sludge and ash produced back to the expansion chamber forfurther processing.

Cooled synthetic gas may be ducted to the base of one or more scrubberunits, each of which may handle an entire flow of gas. To exit from thetop of the scrubber, at least some of the gas passes through a bed ofcages contra-flow to a water spray. During its passage through the bed,both further cooling and scrubbing of the gas resulting in the removalof both soluble and insoluble tars. In some embodiments, at least aportion of the insoluble tars deposit on the ceramic balls, reducing theporosity of the bed, one or more tar cleansing system to regenerate thebed of either unit is included within the supply.

A gas booster, complete with an automatically controlled circulationloop, to ensure gas delivery to downstream users at a consistentpositive pressure, sucks “Clean to use” gas from the scrubbers. Tohandle intermittent changes in gas consumption, preferred embodimentsinclude a gas holding tank 108 included to act as a buffer.

Clean to use gas may then be routed for one or more of: consumption ingas powered turbine engines 107, powering of generators as a source ofenergy; and steam generation to be used within a waste processingfacility. Solid waste is generally sterile and environmentally neutral.

Referring now to FIG. 2A. a pyroliser retort 200A is illustrated alongwith individual controls zones 206 that can provide more efficientoperation of a pyrolysis muffle 208. One or more combustion chambers 203provide thermal energy to the pyrolysis muffle 208. Also shown isresidue exit passage 202

Referring now to FIG. 2B, multiple retorts 200B may be stacked orotherwise aligned to a form a pyrolysis muffle 208. The muffle 208 willinclude an in feed ingress passage 201 and residue exit passage 202.Generally, as described herein, the in feed ingress passage 201 willreceive preheated and pre-processed waste material and the residue exitpassage 202 will pass out carbonized waste. One or more gas take offs205 may be functional to remove gas resulting from the pyrolysistreatment of the waste. Individual control zones 206 may provide moreefficient operation of the pyrolysis muffle 208.

Referring now to FIG. 2C, heating tubes 204 are included to betterdistribute heat throughout the muffle 208 and more efficiently processwaste placed within the muffle.

Referring now to FIG. 2D, according to the present invention a pyroliserretort may include heating or radiation tubes 204. The heating tubes 203provide more uniform and efficient heat distribution within the retort200, as compared to a retort without such radiation tubes 204.

Referring now to FIG. 2E, A perspective view of a pyrolysis unitaccording to the present invention is also illustrated at 207.

Referring now to FIG. 2F a side and perspective view of control zones206 and heating tubes is illustrated.

FIG. 2G illustrates a side view of combustion chambers 203 and residueexit passage 202 is illustrated.

Referring to FIG. 3, an exemplary facility layout is illustrated. Insome embodiments, input feedstock may include mixed municipal waste,sometimes referred to as “black bag” municipal waste due its collectionin black garbage bags. The input feedstock may be delivered to the wastesite by way of container; straight beam truck, barge transport or otherknown means of waste transport. The transported waste is preferablyloaded onto a feed system for conveyance to other portions of theapparatus.

In some embodiments, the feed system may load input mixed wastesequentially into a pressure vessel to compact the mixed waste materialthat is to be processed. Generally, the system efficiency increases ascompaction of feed increases.

Compacted waste is input into pyrolysis chambers and exposed topyrolysis. In the pyrolysis chambers, the waste is exposed to hightemperatures of between 500° C. and 800° C. in an atmosphere of reducedoxygen such that combustion is contained. Following processing of thecompacted waste within the pressure vessels a series of conveyors,screens and separators utilizing various material separation techniquesmay be provided to enable recovery of metals, plastics and glass andother materials.

In some embodiments multiple autoclaves, such as for example sixautoclaves can be used to sterilize the waste used as feed into therenewable energy generation systems of the present invention. Eachautoclave may include a pressure vessel that contains an internal rotarydrum which may extend past the autoclave entrance flange to eliminatecontamination for sealing purposes. In some embodiments, the internaldrum may be supported on wheels positioned within the pressure vesselinitially radial to the autoclave to provide a smooth rotationalmovement. These wheels may be capable of being positioned at up to about90 degrees to allow for withdrawal of the inner drum when desired. Theinlet door of a standard spherical design can be side hinged.

In some embodiments a drive for the autoclave may be engineered on thebasis of a central drive via chain wheel and sprocket around the girthof the inner drum. The pressure vessel may be insulated by way of 100 mmmineral wood providing a heat loss of 100 watts per square meter atmaximum temperature. Drum rotation may be accomplished by way of a motorand gearbox assembly mounted external to the autoclave or alternativehydraulic motor.

In some embodiments a steam generator, such as, for example, a dual fuelboiler may be used in conjunction with the autoclave. By way ofnon-limiting example, a maximum demand on the steam generator can be inthe order of 12,000 kg per hour. Generally, duplexing (pressurizing onevessel while de-pressurizing the other) the demand can be decreased. TheAutoclave may operate, for example, at a pressure of approximately 5.2Bar/160 degrees C. The boiler however, may be designed to charge theaccumulator to a pressure of 17 bar or more.

In some embodiment, an accumulator may be positioned adjacent to the sixautoclaves and provide for a peak demand well in excess of an averagesteam produced by the steam boiler. Some particular examples may includean accumulator vessel capable of storing pressurized hot water atbetween 10 and 25 bar and nominally 17 bar. In addition, some particularembodiments can include an accumulator vessel with dimensions ofapproximately 3.5 m diameter by 13.5 m long.

In some preferred embodiments, shell and tube type condensers areemployed and are close coupled to the system to allow any of thecondensers to operate with either of the autoclaves. Each condenser issized to accommodate initial high volume through to the lower volumenear to pressure equalization. A programmable control valve within thesystem ensures that the condenser is not overloaded at the start of theevacuation process. In some embodiments, a water treatment system mayalso be included to treat water at a flow rate of approximately 20 m³/hr(6 m³ in 20 mins) or more of condensate as it is withdrawn from thecondenser. Discharge from the water treatment system may preferably beof boiler feed water quality.

Cooled water from the autoclave (6 m3/20 mins) may enter one or moreelectro-coagulation units. Each electro-coagulation unit in turn mayinclude one or more ×4 aluminum electrodes and run from a powercontroller. A single controller or redundant controllers may beutilized. Coagulated effluent may be discharged directly to a flotationunit (5 m3 capacity) where solid- liquid separation occurs or otherdischarge route.

In some embodiments, contaminants in the waste stream can be removed viaa mechanical scraper from the top of an electro-flotation unit anddischarged to a sludge tank. Clarified water is available for return toa Return Tank as Boiler Feed water. An ON/OFF control of theelectro-coagulation unit is controlled via a signal from the PLC. Pumpedfeed to the electro-coagulation unit and of final effluent to the returntank is also controlled via the PLC.

Water is condensed from an air scrubber/packed tower. Water from the airscrubber may flow at a rate of about 5 m³/Hr. Chemical oxygen demand ofapproximately 0-1000 mg/l is used for typical MSW purposes.

Air scrubber water (5 m3/hr) enters electro-oxidation units. Each unitincludes ×4 platinum equivalent coated electrodes and run from a single70A power controller. Oxidized effluent is discharged direct to aflotation unit (1 m3 capacity) where solid-liquid separation may occur.Contaminants in the waste stream are removed by a mechanical scraperfrom the top of the Electro-flotation unit and discharged to a sludgetank. Treated water is available for re-cycling.

An oil storage tank with approximate dimensions of 2.5 meters diameterby 3 meters high and a capacity of about 13,500 liters of distillate oilis sized to permit continuous operation of the facility on gas oil, ineither mode of operation, for a period of 24 hours before replenishment.The tank is preferably of the above ground level installation type andemploy gravity feed to the boiler.

Granular media filters are located at the discharge of all condensers toclarify the condensate stream. The filters are adequately sized tohandle a number of condensation cycles and be fitted with a flowmonitoring device to initiate automatic cleansing at the end of a cycle.The back flush, which is typically less than 5% of condensate, can bedischarged to the sludge tank.

An initial condenser serves the dual role of a boiler feed waterpre-heater. It is of shell and tube construction and can be operated, onthe tube side, as a single or multiple pass units to suit the operatingmode of the autoclave. Preheated feed water can be discharged into thehot feed water reservoir until its maximum level had been achieved. Atthis juncture, the bypass valve would open and surplus feed-coolingwater can be returned to the cold feed water tank.

To accommodate the significantly different cooling loads between the twomodes of operation and prevent overloading of the feed waterpre-heater—condenser, the timing of the opening speed of thepneumatically operated flow control valves can be adjustable.

To accommodate the significantly different cooling loads between the twomodes of operation, the final condenser would permit direct and/orindirect cooling of the exhaust stream. That is, the unit can be ofshell and tube form with an additional spray feature. With theautoclaves operating in the cascade mode, only the shell and tubeconfiguration can be employed. When operating in the non cascade mode,only sufficient direct contact cooling water can be used to achieve theadditional cooling required.

A mixed bed, such as, for example a cation-anion exchange resin bed,purifies reclaimed condensate and raw municipal make up water to boilerfeed water quality. The purified water is fed to the cold feed waterreservoir until it has been refilled. The unit then automaticallyreverts to its regeneration mode. After regeneration with acid and analkali, the resins may be rinsed and the bed remixed with compressedair.

A hot feed water tank, with a capacity of approximately 6000 liters, islocated adjacent to the boiler and receives pre-heated water from theinitial condenser. The tank is insulated and includes a vent toatmosphere to permit degassing of the boiler feed water. To bothincrease the feed water temperature and compensate for heat losses, thetank is connected to the feed water heater. The tank is fitted with alevel indicator and high and low level switches.

A feed water heater of tubular construction is located in the exhaustflue from the boiler and connected to the hot feed water tank.Circulation of water through the system is by natural convection.

The cold feed water tank, of approximately 10,000 liters capacity isrefilled via a de- ionization plant and provides water to the shell andtube condensers. It is equipped with level switches to controlrefilling. Upon evacuation of hot vapors from an autoclave, water ispumped from one end of the tank to the condensers. Once the hot feedwater tank has been refilled, surplus feed water from the condensers isreturned to the other end of the tank. To minimize mixing of thereturned warm water with the remaining cold water, the tank is fittedwith internal partitions along its length.

Located above the cold water feed tank, may be a set of air blastcoolers with a total cooling capacity of approximately 50/H. Water fromthe hot end of the cold water feed tank is pumped through the coolingtubes and returned to the cold end of the tank. Each cooler is fittedwith a high volume, axial flow fan, which blows oil over the coolingtubes.

Condensate, after passage through the filters is piped to the hot well,which is fitted with high and low level switches. A sump pump dischargeswater from the well to the raw water holding tank.

A holding tank, with a capacity of about 5000 liters, can be installedadjacent to the deionization plant to provide it with its main source ofwater. The tank can be fitted with a low level switch to ensure acontinuous supply of water to the deionization plant from the municipalsupply.

A fine filter can be located upstream of the deionization plant topolish the water quality to that unit. The filter can be of the duplextype and equipment with a differential pressure switch to advise offouling level.

Although the boiler can be supplied with high purity feed water, overtime the total dissolved solids may increase. To monitor this conditionthe conductivity of the boiler water can be continuously monitored.

In some embodiments the boiler can be equipped with a blow down receiverto permit the venting of hot boiler water for T.D.S. adjustment. Ventingwould occur subsequent to autoclave pressurization and the vented water,after cooling, can be returned to the raw water tank for recyclingthrough the deionizer.

In some embodiments the steam supply to each autoclave can be via asteam ejector. When the autoclaves were operating in the cascade modeand subsequent to pressure equalization, steam vapor from the processedautoclave can be recycled into the green autoclave duringpressurization. This may significantly reduce the cooling load on thecondensers and improve overall plant efficiency.

Back flush water from the granular filters is pumped to the sludge tank,which has a capacity of approximately 500 liters, where heavierparticles settle out naturally by virtue of gravitation. Coagulation ofthe finer particles into heavier more dense ones is achieved by electrokinetics. Once the filtrate has clarified it is pumped to the hot wellvia a granular bed filter. The resulting sludge can either be consignedto the landfill fraction or “black bagged” for recycling through theprocess.

Prior to pressurization, the pressure in the autoclave is reduced toless than 100 mb absolute pressure by liquid ring vacuum pumps with atotal capacity of about 3000 m³/h in less than 15 minutes.

Subsequent to pressurization, the same vacuum system is employed toevacuate the steam and remaining non-condensable gases from theautoclave. Commensurate with the reduction in pressure, condensateabsorbed by the waste during pressurization may flash to steam and beextracted by the vacuum pumps. Hence with the re-attainment of the 100mb A pressure, the average temperature of the waste is slightly aboveambient and the moisture content slightly in excess of that of the greenwaste.

To achieve an optimum in energy utilization, an economizer is located inthe exhaust flue down steam of the feed water heater to preheat theboiler burner combustion air. After the vacuum depletion and upon theopening of the autoclave door, the autoclave can be reconnected to thevacuum system to ensure that an air flow into the autoclave from ambientis maintained during unloading to avoid the release of a plume.

A continuous flow of water can be employed to maintain the liquid ringwhich can be discharged, along with the non condensables, into aseparator. The water can be fed from the separator to the hot wellwhereas the non condensables can be ducted to the odor control device.

To remove undesirable odors from the non condensable gas steam prior todischarge to atmosphere, the gases can be passed through an absorptiontower. Whilst current thinking is to employ a packed tower, employingcarbon Raschig rings, with a counter-flow water sprays, PTE may be nottotally convinced that this represents the optimum solution. PTE,therefore propose the packed tower approach provisionally and maycontinue research on this aspect such that after consultation a finaldecision on the most efficient solution can be made.

Free standing, un-insulated steel stacks can vent boiler flue gases andde-odorized autoclave exhaust gases to atmosphere. Generally, the stacksare designed to suit local atmospheric conditions and municipal by-laws.(WID compliance)

Pneumatically operated flow control and shut off valves of the butterflyand ball type can be provided where appropriate to fully automate theinstallation. All automated shut off valves can be provided with manualvalve bypasses. Butterfly valves, used on vacuum or steam lines wouldemploy elastomer seals to ensure gas tight closure.

Valves in vacuum and high pressures lines provide to allow an autoclaveto be isolated from the system for maintenance purposes is of thelockable closed type.

All piping for fluids at pressures in excess of 10 kPa is preferablyseamless to the appropriate pressure classification and fluid colorcoded to International Standards. Piping in excess of 2″ NB is flanged.

With the exception of the boiler/accumulator feed water pumps, all pumpsis of the direct connected, centrifugal type with mechanical seals. Theboiler feed water pumps include positive displacement piston pumps.

Totalizing meters, with manual bypasses can be located in both the oiland LPG (liquefied petroleum gas) supply manifold to the boiler.Pressure gauges and temperature gauges, mounted in thermowells, monitorgas and oil pressure to the burner, boiler water temperature andpressure combustion air pressure and flue gas exhaust temperature. Alevel gauge would indicate water level in the boiler shell.

Both autoclaves and the accumulator are fitted with pressure andtemperature transmitters to permit monitoring and control of the processvia the PLC/Scada. In addition, the accumulator is fitted with high andlow level switches to control water level.

Fiber to Energy

The fiber produced is transferred, for example, by way of standardtraversing conveyor to the input silo of the 2 dryers. The PLCcontrolled metering system may alternatively progress the RDF fiber intothe dryers at a pre-determined rate. A special designed thermalcombustion chamber is positioned in front of the dryer.

Hot gases from the engines are progressed through to this chamber andmay provide the primary energy input for the system.

Following exit from the dryer the RDF is progressed through to thepre-pyrolizer systems from where the material is progressed through thepyrolizer in order to produce the gas. The resultant gas may be used todrive gas engines or any other combustion system.

Two standard thermal rotating drum dryers is employed, each designed totake 60% of the throughput capacity. From examination of the dryer P &I.D. it may be seen that the system is based on the use of twoconcentric drums, each with internal flights thus providing for materialcharge and discharge at the same end.

Each sealed charge/discharge cuff with a negative pressure seal mayensure material containment. The drive may be accomplished by way ofchain driven girth gear, connected to a bed motor system. A variablespeed drive is connected with a PLC/Scada System. The dryer receivingsilo and charge chute is formed as an integral part of the charge cuff,thus resulting in only one seal for the rotating drum.

A refractory lined heat input chamber is positioned in front of eachdryer. The main heat input is drawn through by the ID (induced draft)fan from the collection manifold of the engine exhausts. Supplementaryheat input to provide for precise control at the dryer exit is by way ofa dual fuel burner designed to operate on the client's selected gas andthe exhaust gas produced by the pyrolysis units. Off cyclones, bagfilter, complete with pulsing system and exhaust gas, ID fan may formpart of the dryer package.

In order to accommodate approximately 21 tons per hour, or more of dryfiber (23.3 tons at 10% moisture) multiple units, such as, for example,a battery of seven units may be installed. Each unit can be completewith six zone vertical tower pyrolysis units and 2, pyrolysis unitsystems.

Each zone has it's own dual fuel combustion system, suitable foroperating on the client's LPG (liquefied petroleum gas) or natural gasor synthetic fuel produced by the system.

Each unit may have it's own dedicated gas booster and scrubber fromwhich the gas is progressed, through to a ring main system.

The ash handling system from each pyrolization tower is progressed to acontrol ash screw, which may progress through to two main plantdischarge screws to provide for alternate discharge into road container.

Platforms and support structure manufactured from rolled steel sectionsmay provide support and access to individual items of equipment.

Each of the pyrolysis units can be connected through to a gasometerwhich may accommodate varying gas volume, thus providing for maximum useof the gas, on a priority basis to the steam boilers, pyrolysis units,dryers and thence to the gas engines on a progressive basis to engines 1to 7.

Off thermal oxidizers are connected through to a single exhaust stack toprovide for a single emission point.

Referring to FIG. 3, a block diagram of some aspects of the presentinvention is illustrated. In some embodiments, input feedstock mayinclude mixed municipal waste 301, sometimes referred to as “black bag”municipal waste due its collection in black garbage bags. The inputfeedstock may be delivered to the waste site by way of container;straight beam truck, barge transport or other known means of wastetransport. The transported waste is preferably loaded onto a feed systemfor conveyance to other portions of the apparatus.

In some embodiments multiple autoclaves 302, such as for example sixautoclaves 302 can be used to sterilize the waste used as feed into therenewable energy generation systems of the present invention. Eachautoclave 302 includes a pressure vessel that contains an internalrotary drum which may extend past the autoclave entrance flange toeliminate contamination for sealing purposes. In some embodiments, theinternal drum may be supported on wheels positioned within the pressurevessel initially radial to the autoclave to provide a smooth rotationalmovement. These wheels may be capable of being positioned at up to about90 degrees to allow for withdrawal of the inner drum when desired. Theinlet door of a standard spherical design can be side hinged.

In some embodiments a drive for the autoclave 302 may be engineered onthe basis of a central drive via chain wheel and sprocket around thegirth of the inner drum. The pressure vessel may be insulated by way of100 mm mineral wood providing a heat loss of 100 watts per square meterat maximum temperature. Drum rotation may be accomplished by way of amotor and gearbox assembly mounted external to the autoclave oralternative hydraulic motor.

In some embodiments a steam generator, such as, for example, a dual fuelboiler may be used in conjunction with the autoclave. By way ofnon-limiting example, a maximum demand on the steam generator can be inthe order of 3,000 kg per hour. Generally, duplexing (pressurizing onevessel while de-pressurizing the other) the demand can be decreased. TheAutoclave may operate, for example, at a pressure of approximately 5.2Bar/160 degrees C. The boiler however, may be designed to charge theaccumulator to a pressure of 17 bar or more.

In some embodiment, an accumulator may be positioned adjacent to the sixautoclaves and provide for a peak demand well in excess of an averagesteam produced by the steam boiler. Some particular examples may includean accumulator vessel capable of storing pressurized hot water atbetween 10 and 25 bar and nominally 17 bar. In addition, some particularembodiments can include an accumulator vessel with dimensions ofapproximately 3.5 m diameter by 13.5 m long.

In some preferred embodiments, shell and tube type condensers areemployed and are close coupled to the system to allow any of thecondensers to operate with either of the autoclaves. Each condenser issized to accommodate initial high volume through to the lower volumenear to pressure equalization. A programmable control valve within thesystem ensures that the condenser is not overloaded at the start of theevacuation process. In some embodiments, a water treatment system mayalso be included to treat water at a flow rate of approximately 20 m³/hr(6 m³ in 20 mins) or more of condensate as it is withdrawn from thecondenser. Discharge from the water treatment system may preferably beof boiler feed water quality.

Cooled water from the autoclave (6 m3/20 mins) may enter one or moreelectro-coagulation units. Each electro-coagulation unit in turn mayinclude one or more ×4 aluminum electrodes and run from a powercontroller. A single controller or redundant controllers may beutilized. Coagulated effluent may be discharged directly to a flotationunit (5 m3 capacity) where solid- liquid separation occurs or otherdischarge route.

In some embodiments, contaminants in the waste stream can be removed viaa mechanical scraper from the top of an electro-flotation unit anddischarged to a sludge tank. Clarified water is available for return toa Return Tank as Boiler Feed water. An ON/OFF control of theelectro-coagulation unit is controlled via a signal from the PLC. Pumpedfeed to the electro-coagulation unit and of final effluent to the returntank is also controlled via the PLC.

Water is condensed from an air scrubber/packed tower. Water from the airscrubber may flow at a rate of about 5 m³/Hr. Chemical oxygen demand ofapproximately 0-1000 mg/l is used for typical MSW purposes.

Air scrubber water (5 m3/hr) enters electro-oxidation units. Each unitincludes ×4 platinum equivalent coated electrodes and run from a single70A power controller. Oxidized effluent is discharged direct to aflotation unit (1 m3 capacity) where solid- liquid separation may occur.Contaminants in the waste stream are removed by a mechanical scraperfrom the top of the Electro-flotation unit and discharged to a sludgetank. Treated water is available for re-cycling.

An oil storage tank with approximate dimensions of 2.5 meters diameterby 3 meters high and a capacity of about 13,500 liters of distillate oilis sized to permit continuous operation of the facility on gas oil, ineither mode of operation, for a period of 24 hours before replenishment.The tank is preferably of the above ground level installation type andemploys gravity feed to the boiler.

Granular media filters are located at the discharge of all condensers toclarify the condensate stream. The filters are adequately sized tohandle a number of condensation cycles and be fitted with a flowmonitoring device to initiate automatic cleansing at the end of a cycle.The back flush, which is typically less than 5% of condensate, can bedischarged to the sludge tank.

An initial condenser serves the dual role of a boiler feed waterpre-heater. It is of shell and tube construction and can be operated, onthe tube side, as a single or multiple pass units to suit the operatingmode of the autoclave. Preheated feed water can be discharged into thehot feed water reservoir until its maximum level had been achieved. Atthis juncture, the bypass valve would open and surplus feed-coolingwater can be returned to the cold feed water tank.

To accommodate the significantly different cooling loads between the twomodes of operation and prevent overloading of the feed waterpre-heater—condenser, the timing of the opening speed of thepneumatically operated flow control valves can be adjustable.

To accommodate the significantly different cooling loads between the twomodes of operation, the final condenser would permit direct and/orindirect cooling of the exhaust stream. That is, the unit can be ofshell and tube form with an additional spray feature. With theautoclaves operating in the cascade mode, only the shell and tubeconfiguration can be employed. When operating in

A hot feed water tank, with a capacity of approximately 6000 liters, islocated adjacent to the boiler and receives pre-heated water from theinitial condenser. The tank is insulated and includes a vent toatmosphere to permit degassing of the boiler feed water. To bothincrease the feed water temperature and compensate for heat losses, thetank is connected to the feed water heater. The tank is fitted with alevel indicator and high and low level switches.

A feed water heater of tubular construction is located in the exhaustflue from the boiler and connected to the hot feed water tank.Circulation of water through the system is by natural convection.

The cold feed water tank, of approximately 10,000 liters capacity isrefilled via a de- ionization plant and provides water to the shell andtube condensers. It is equipped with level switches to controlrefilling. Upon evacuation of hot vapors from an autoclave, water ispumped from one end of the tank to the condensers. Once the hot feedwater tank has been refilled, surplus feed water from the condensers isreturned to the other end of the tank. To minimize mixing of thereturned warm water with the remaining cold water, the tank is fittedwith internal partitions along its length.

Located above the cold water feed tank, may be a set of air blastcoolers with a total cooling capacity of approximately 5 GJ/H. Waterfrom the hot end of the cold water feed tank is pumped through thecooling tubes and returned to the cold end of the tank. Each cooler isfitted with a high volume, axial flow fan, which blows oil over thecooling tubes.

Condensate, after passage through the filters is piped to the hot well,which is fitted with high and low level switches. A sump pump dischargeswater from the well to the raw water holding tank.

A holding tank, with a capacity of about 5000 liters, can be installedadjacent to the deionization plant to provide it with its main source ofwater. The tank can be fitted with a low level switch to ensure acontinuous supply of water to the deionization plant from the municipalsupply.

A fine filter can be located upstream of the deionization plant topolish the water quality to that unit. The filter can be of the duplextype and equipment with a differential pressure switch to alert offouling level.

Although the boiler can be supplied with high purity feed water, overtime the total dissolved solids may increase. To monitor this conditionthe conductivity of the boiler water can be continuously monitored.

In some embodiments the boiler can be equipped with a blow down receiverto permit the venting of hot boiler water for T.D.S. adjustment. Ventingwould occur subsequent to autoclave pressurization and the vented water,after cooling, can be returned to the raw water tank for recyclingthrough the deionizer.

In some embodiments the steam supply to each autoclave can be via asteam ejector. When the autoclaves were operating in the cascade modeand subsequent to pressure equalization, steam vapor from the processedautoclave can be recycled into the green autoclave duringpressurization. This may significantly reduce the cooling load on thecondensers and improve overall plant efficiency.

Back flush water from the granular filters is pumped to the sludge tank,which has a capacity of approximately 500 liters, where heavierparticles settle out naturally by virtue of gravitation. Coagulation ofthe finer particles into heavier more dense ones is achieved by electrokinetics. Once the filtrate has clarified it is pumped to the hot wellvia a granular bed filter. The resulting sludge can either be consignedto the landfill fraction or “black bagged” for recycling through theprocess.

Prior to pressurization, the pressure in the autoclave is reduced toless than 100 mb absolute pressure by liquid ring vacuum pumps with atotal capacity of about 3000 m³/h in less than 15 minutes.

Subsequent to pressurization, the same vacuum system is employed toevacuate the steam and remaining non-condensable gases from theautoclave. Commensurate with the reduction in pressure, condensateabsorbed by the waste during pressurization may flash to steam and beextracted by the vacuum pumps. Hence with the re-attainment of the 100mb A pressure, the average temperature of the waste is slightly aboveambient and the moisture content slightly in excess of that of the greenwaste.

To achieve an optimum in energy utilization, an economizer is located inthe exhaust flue down steam of the feed water heater to preheat theboiler burner combustion air. After the vacuum depletion and upon theopening of the autoclave door, the autoclave can be reconnected to thevacuum system to ensure that an air flow into the autoclave from ambientis maintained during unloading to avoid the release of a plume.

A continuous flow of water can be employed to maintain the liquid ringwhich can be discharged, along with the non condensables, into aseparator. The water can be fed from the separator to the hot wellwhereas the non condensables can be ducted to the odor control device.

To remove undesirable odors from the non condensable gas steam prior todischarge to atmosphere, the gases can be passed through an absorptiontower. Whilst current thinking is to employ a packed tower, employingcarbon Raschig rings, with a counter-flow water sprays.

Free standing, un-insulated steel stacks can vent boiler flue gases andde-odorized autoclave exhaust gases to atmosphere. Generally, the stacksare designed to suit local atmospheric conditions and municipal by-laws.

Pneumatically operated flow control and shut off valves of the butterflyand ball type can be provided where appropriate to fully automate theinstallation. All automated shut off valves can be provided with manualvalve bypasses. Butterfly valves, used on vacuum or steam lines wouldemploy elastomer seals to ensure gas tight closure.

Valves in vacuum and high pressure lines can be provided to allow anautoclave to be isolated from the system for maintenance purposes is ofthe lockable closed type.

All piping for fluids at pressures in excess of 100 kPa is preferablyseamless to the appropriate pressure classification and fluid colorcoded to International Standards. Piping in excess of 2″ NB is flanged.

With the exception of the boiler/accumulator feed water pumps, all pumpsare of the direct connected, centrifugal type with mechanical seals. Theboiler feed water pumps include positive displacement piston pumps.

Totalizing meters, with manual bypasses can be located in both the oiland LPG (liquefied petroleum gas) supply manifold to the boiler.Pressure gauges and temperature gauges, mounted in thermowells, monitorgas and oil pressure to the burner, boiler water temperature andpressure combustion air pressure and flue gas exhaust temperature. Alevel gauge would indicate water level in the boiler shell.

Both autoclaves and the accumulator are fitted with pressure andtemperature transmitters to permit monitoring and control of the processvia the PLC/Scada. In addition, the accumulator is fitted with high andlow level switches to control water level.

The fiber produced 303 is transferred, for example, by way of standardtraversing conveyor to input a silo of dryers 304. The PLC controlledmetering system may alternatively progress the RDF fiber 303 into thedryers 304 at a pre-determined rate. A special designed thermalcombustion chamber is positioned in front of the dryer 304.

Hot gases 305 from the engines are progressed through to this chamberand may provide primary energy input for a turbine system 306.

Following exit from a dryer 304 the RDF is progressed through to thepre-heating systems from where the material is progressed through thepyrolizer in order to produce the gas 305. The resultant gas 305 may beused to drive gas turbines 306 and or other engines or any othercombustion system. The turbines may be used to power electricalgenerators and provide electrical power to the grid 307.

Two standard thermal rotating drum dryers are employed; each designed totake 60% of the throughput capacity. From examination of the dryer P &I.D. it may be seen that the system is based on the use of twoconcentric drums, each with internal flights thus providing for materialcharge and discharge at the same end.

Each sealed charge/discharge cuff with a negative pressure seal mayensure material containment. The drive may be accomplished by way ofchain driven girth gear, connected to a bed motor system. A variablespeed drive is connected with a PLC/Scada System. The dryer receivingsilo and charge chute is formed as an integral part of the charge cuff,thus resulting in only one seal for the rotating drum.

A refractory lined heat input chamber is positioned in front of eachdryer. The main heat input is drawn through by the ID (induced draft)fan from the collection manifold of the engine exhausts. Supplementaryheat input to provide for precise control at the dryer exit is by way ofa dual fuel burner, designed to operate on the client's selected gas,and the exhaust gas produced by the pyrolysis units. Cyclones, bagfilter, complete with pulsing system and the exhaust gas ID fan may formpart of the dryer package.

Each multi zoned muffle section of the pyroliser has its own dual fuelcombustion system, suitable for operating on the client's LPG (liquefiedpetroleum gas), natural gas or the synthetic fuel produced by thesystem.

Each unit may have its own dedicated gas booster and gas scrubber fromwhich the gas is progressed, through to a ring main system.

The residue handling system from each pyrolization tower is progressedto a controlled screw, which may progress through to two main plantdischarge screws to provide for alternate discharge into road container.

Platforms and a support structure manufactured from rolled steelsections may provide support and access to individual items ofequipment.

Each of the pyrolysis units can be connected through to a gas holder orholders, which will accommodate varying gas volume, thus providing formaximum use of the gas, on a priority basis to the steam boilers,pyrolysis units, dryers and thence to the gas engines on a progressivebasis.

A number of thermal oxidizers are connected through to a single exhauststack to provide for a single emission point if practical.

Conclusion

A number of embodiments of the present invention have been described.Nevertheless, it will be understood that various modifications may bemade to the process surrounding the pre-conditioning and pyrolysis unitwithout departing from the spirit and scope of the invention. Forexample, various methods or equipment may be used to implement theprocess steps described herein or to create a device according to theinventive concepts provided above and further described in the claims.In addition, the integration of various components, as well as softwareand firmware, may be implemented. Accordingly, other embodiments arewithin the scope of the following claims.

1. A method of treating municipal solid waste, the method comprising:conveying said municipal solid waste comprising one or both of inorganicmaterial and organic material into a pre-conditioner unit; heating saidmunicipal solid waste in said pre-conditioner unit sufficiently toessentially sterilize at least a majority of said municipal solid waste;separating inorganic materials from the organic materials; exposing theorganic material to an environment of saturated steam; heating theenvironment of saturated steam containing the organic matter to atemperature of 160° C. or more; and producing a gaseous by-product byway of the heating of the organic material in an environment of depletedoxygen at about 700° C. or more.
 2. The method of claim 1 additionallycomprising the step of separating inert materials including ferrous andnon ferrous materials; glass and stone from the inorganic materials fromthe organic materials.
 3. The method of claim 2 wherein the organicmaterial comprises one or more of: cellulosic flakes, wood and textiles.4. The method of claim 2 wherein the inorganic material comprises one orboth of aluminum and magnetic metals.
 5. The method of claim 1 whereinthe step of heating said municipal solid waste in said pre-conditionerunit comprises placing the municipal solid waste in a chamber comprisinga temperature of between about 400° C. and 600° C. to generatepretreated municipal waste.
 6. The method of claim 1 additionallycomprising the step of passing the pretreated municipal waste through aheated multi-zoned pyrolysis muffle chamber.
 7. The method of claim 6additionally comprising the step of providing heat through radiant tubeswithin the multi-zoned pyrolysis muffle chamber.
 8. The method of claim7, wherein the heat provided through the radiant tubes promotespyrolysis of the municipal waste.
 9. The method of claim 8 additionallycomprising the step of generating synthetic gas as a result of thepyrolysis of the municipal waste.
 10. The method of claim 9 additionallycomprising the step of passing the synthetic gas through gas take offports in gaseous communication with the multi-zoned pyrolysis mufflechamber.
 11. The method of claim 10 additionally comprising the step ofcooling said synthetic gas in a cooling chamber.
 12. The method of claim11 additionally comprising the step of cooling the cooling chamber viacirculation of a coolant in thermal communication with said coolingchamber.
 13. The method of claim 12 wherein said coolant in an aqueoussolution.
 14. The method of claim 13, additionally comprising the stepof scrubbing the synthetic gas via a gas scrubber.
 15. The method ofclaim 10 additionally comprising the step of conveying condensed tar andoil to a collector, wherein the condensed tar and oil result fromplacing the organic material in the pyrolysis chamber.